Geissbuehler, MatthiasKadlecova, ZuzanaKlok, Harm-AntonLasser, Theo2012-09-132012-09-132012-09-13201210.1364/BOE.3.002526https://infoscience.epfl.ch/handle/20.500.14299/85384WOS:000309557700017An optical method is presented that allows the measurement of the triplet lifetime of a fluorescent molecule. This is a characteristic specific to each fluorophore. Based on differences in triplet lifetimes of two fluorescent species (autofluorescence versus label), this novel approach measures relative quantities of a transmembrane receptor and associated fluorescently labeled ligand during its recycling in living cells. Similarly to fluorescence-lifetime based methods, our approach is almost insensitive to photobleaching. A simple theory for unmixing two known triplet lifetimes is presented along with validation of the method by measurements of transferrin recycling in a model system based on chinese hamster ovarian cells (CHO). Transferrin is the delivery carrier for Fe3+ to the cell.Fluorescence microscopyLifetime-based sensingImage analysisFunctional monitoring and imagingMedical and biological imagingBiologyMicroscopytext::journal::journal article::research article